The present invention relates to periodontal probes and in particular to such probes useful for determining the attachment point of tissue to a tooth.
The investigation of gum disease is becoming increasingly important in dental care. The monitoring of the disease and a quantitative assessment of the effect of treatment on the disease has, however, been difficult to accomplish in an objective manner. One existing technique is to measure the depth of the pocket that forms between a tooth and the gum and to monitor variations in that pocket depth as an indication of the effectiveness of the treatment. However, the depth of the pocket may not be particularly significant as it can vary with changes in the inflammation of the gum tissue. What does however appear to be significant is determining the location of the attachment point to the tooth and any changes in this attachment point.
Previous attempts to measure accurately the attachment point of the tooth have utilised a manual probe. Direct measurement to a reference datum on the tooth with a manual probe has not been possible because a probe having an overall length in the order of 30 mm would be required. This, however, would not be manoeuvrable in the mouth of a patient. Accordingly, the manual monitoring process used to date requires a stent to be made with a reference datum marked on the stent. It is then possible to measure the distance from the datum on the stent to the point of attachment with a manual probe that need only be in the order of 12 mm long. The provision of a stent is, however, time-consuming and of course relatively expensive but more significantly the measuring technique appears to be open to error. Firstly, the reading of the calibration marks on the probe against the datum mark is open to error and there is inevitably a tendency to vary the force exerted on the manual probe so that the degree of penetration of the tip of the probe into the gum tissue will vary. This will inevitably introduce inaccuracies in the measuring technique.
It has been proposed to overcome some of these disadvantages by using an automated retractable probe that is advanced to the bottom of the pocket and then retracts, seeking to detect the surface irregularities caused by the cemento/enamel junction. The amount of retraction is then used as an indication of the attachment point of the pocket. However, in practice the detection of the cemento/enamel junction may be obscured by other background noise and it would not appear that there has been any attempt to overcome the problem of accurately and repeatedly determining the bottom of the pocket.
According to the present invention there is provided an apparatus for determining the attachment point of tissue to a tooth comprising:
a body for insertion into the mouth;
a datum surface on said body for engagement with a location on the tooth;
a probe moveable relative to said datum surface into engagement with said tissue;
drive means operable upon said probe to control movement thereof;
measuring means to measure movement of said probe relative to said datum surface, said drive means including force control means to regulate the force applied by said drive means to said probe to maintain said force at a predetermined value; and
attitude sensing means located on said body for inhibiting operation of said measuring means upon movement of said body from predetermined a attitude, thereby permitting movement of said probe when said body is positioned in any attitude whilst inhibiting the measuring of such movement of said probe until said body is positioned in said predetermined attitude while allowing the measuring of movement once said body is positioned in said predetermined attitude.
By providing a constant force for the advancement of the probe, the bottom of the pocket will be repeatedly determined giving consistent measurements.
Furthermore, the provision of the attitude sensing device avoids inaccuracies in measurements due to misalignment of the probe relative to the tooth.
It is further preferred that the drive is remote from the body of the probe so that the dimensions of the probe are maintained at a minimum.